The proposed research program addresses human responses to the thermal environment in health and disease. Climate, season and weather are considerably attenuated by clothing, buildings and indoor climate control, but significant effects on morbidity and mortality remain. Winter mortality is 20-30% higher than the summer values; heat waves and cold waves can cause a doubling of daily mortality in many areas. Well-coordinated field and laboratory studies will address the mechanisms involved in these effects. The thermal environment will be characterized by engineers and physiologists in terms of the combined effects of clothing, building and environmental control systems. Physiologists will study the phenomena and mechanisms of acclimation and acclimatization which allow man to adapt to a long-term, thermally stressful condition, as well as the range and distribution of physiological responses in different parts of the population. The effects of different thermal environments in terms of behavioral response such as thermal sensation, acceptability and work productivity will be studied by psychologists, physiologists and engineers. Having developed insights in the modifying effects of clothing, buildings and environmental control the relationship between climate, season and weather, and mortality and morbidity will be studied by epidemiologists, physiologists and biostatisticians. Changes in rates of fresh air intake and ventilation are important among strategies for energy conservation with consequences for the quality of the indoor environment, including its thermal characteristics. Engineers and psychologists will study the potential effects of such changes on health and well-being. The thermal and non-thermal effects of microwaves will be studied in non-human primates using a combination of physiological and behavioral techniques. Significant outcomes of this program could include a better understanding of the effects of the thermal environment, identification of vulnerable segments of the population, strategies for effective protection of such vulnerable indviduals and methods to evaluate public health consequences of energy conservation strategies.